1. Field of the Invention
This invention relates to prevention and cleanup of spills, and more particularly relates to a composition for converting a liquid to a gel which is useful in prevention or cleanup of spills.
2. Background of the Invention
Many occasions arise when it is necessary to clean up a spilled liquid. It is common practice to add a material capable of absorbing many times its weight of liquid without dissolving in the liquid. In this way, the spill may be cleaned up essentially by sweeping or vacuuming a solid. A variety of liquid absorbents are commercially available for this purpose.
Spills are of particular concern in the medical arena. There is a general apprehension on the part of public health officials worldwide concerning spilled body fluids potentially contaminated with hepatitis, AIDS or other infectious diseases. A particular area of concern arises in surgical procedures which often require body fluids to be drained from the patient.
For drainage of body fluids during surgery, suction canisters are used. In general, suction canisters employ a collection system and a vacuum source, such as a pump, to facilitate this drainage procedure. Each canister generally includes a flexible line or hose connected to the vacuum source so that vacuum can be applied to the interior of the canister. Another flexible line or hose extends from the canister to the source of body fluids in the patient. Once the vacuum is applied, a negative pressure gradient is communicated through the interior of the suction canister so that body fluids are drawn into the canister. Suction canisters and structure allowing multiple units to be connected in series is disclosed in U.S. Pat. No. 4,384,580 to Leviton.
Upon completion of the surgery, the canister containing the waste fluids must be discarded in a safe and environmentally sound way. This often requires storing and transporting canisters filled with liquids, a procedure fraught with the possibility of leaks and spills. It has become common practice in the art to add a material to the canister to convert the liquid to a solid or semisolid so that, if an accident should occur, any spill will be confined to the immediate area and cleanup will be quicker and safer.
For this purpose, gelling agents have been used. Gelling agents, in granular form, imbibe water, swell to many times their original size and fix the entire highly solvated intermolecular bonds. Cullen, in U.S. Pat. No. 4,748,069, discloses a packet containing sodium polyacrylate. When placed in a suction canister containing body fluids, the packet degrades so that the polyacrylate comes into contact with and immobilizes the fluid as a gel. Commercial products using polyacrylate gelling agents for suction canisters are RED-Z.TM. (Medzam, Ltd., North Tonowanda, New York), and LIQUISORB.RTM. (American Colloid Co., Arlington Heights, Ill.).
Starch is a polymer having repeating carbohydrate units which occurs in abundance in many plants. Commercial sources are corn, potatoes, tapioca, rice and wheat. Starch is well-known to undergo irreversible gellation in hot water, but is insoluble in cold water. Gellation in water at room temperature, however, can be induced by chemical modification.
The term modified starch refers to a product which is water soluble and forms a gel at room temperature. Modified starches are formed from starch by acetylation, chlorination, hydrolysis or enzymatic treatment of the starch and are used as textile sizing agents and paper coatings. Starch derivatized with carboxylate, sulfonate or sulfate groups forms alkali metal and ammonium salts which form nongelling dispersions of high viscosity. Crosslinking of the carbohydrate groups gives high viscosity products useful as thickeners.
Starch may also be modified to absorb liquid at room temperature by graft polymerization of hydrophilic groups. Highly absorbent products consisting of starch modified with pendent grafted acrylonitrile, acrylamide and sodium acrylate groups are disclosed in U.S. Pat. Nos. 3,661,815 and 4,302,369 and are available from Grain Processing Corp., Muscatine, Iowa, under the trade name WATER-LOCK.RTM..
Silicone treated starches are known. Gelatinized starch granules treated with a silicone oil and coated with wax are disclosed to be suds control agents in U.S. Pat. No. 4,451,387. U.S. Pat. No. 4,818,292 discloses particles of swollen hydrated hydrophilic starch coated with silicone oil as an antifoam additive for detergent powders. In U.S. Pat. No. 3,491,036, starch is rendered hydrophobic by treatment with a silicone resin and used as an anti-offset agent in printing. Starch treated with organosiloxane polymers are disclosed to be useful as a glue, binder, filler or coating in U.S. Pat. No. 4,495,226.
Modified starches form gels rapidly in cold water and have a very high ultimate capacity for liquid absorption, but have the drawback that clumping occurs on initial contact of the granules with water. The clumps have a barrier of gelled starch surrounding ungelatinized granules. Because of clumping, a long time is required for maximum water absorption. There is a need for a starch modified to overcome this deficiency and render inexpensive starch useful as an effective gelling agent. The present invention fulfills this need.